Systems have been devised in recent years for recording high frequency information on a storage medium and for attaining a subsequent reproduction of the information from the storage medium. For example, information has been recorded on a magnetic tape where the information constitutes video and audio signals having characteristics which respectively represent at each instant an image being viewed and the sounds emanating from the environment of the image. Signals are also recorded on storage media in representation of different scientific and mathematical information, including the readings of instruments and the values obtained from computations performed by digital computers.
For the recording of high frequency information, the systems now in use generally employ magnetic tapes as the storage medium. These tapes have, in general, proved fairly satisfactory in recording signals representative of information and in obtaining the reproduction of the information. However, the fidelity of the recording and reproduction is dependent upon the magnetic structure of the tape so that the magnetic tapes have to be manufactured with considerable precision. However, the information recorded on the magnetic tapes has a limited density of information packing so that a relatively great amount of tape is required to store the information represented, for example, by a television program having a duration of approximately a half hour. The limited density of information packing on the tape has resulted from limitations in the speed of response of the magnetic transducer heads which are disposed in contiguous relationship to the tape. It has also resulted from limitations in the frequency at which information can be transferred between the magnetic transducer heads and the magnetic layers on the tape.
The systems now in use generally dispose the transducing head adjacent to the tape to record information in magnetic form on the tape and to reproduce such magnetic information as electrical signals from the tape. The adjacent relationship between the transducing head and the tape causes the tape to rub occasionally against the head so that magnetic particles become removed from the tape and are deposited on the head to affect the operation of the head. The magnetic particles removed from the tape also tend to produce an abrasive action on the head so that the response characteristics of the head become permanently affected.
It is difficult to use a magnetic tape as a master for the reproduction of a large quantity of identical tapes because of the wear on the tape and the adjacent heads and because of the considerable length of the tape required for the master.
Systems using discs as the master would probably be more desirable than tapes since they tend to store information in a more compact form than tapes. However, the disc systems of the prior art have generally involved a groove cut in a disc of plastic material, with variations in the walls of the groove representing the electrical information.
The disc systems of the prior art have had certain important deficiencies. For example, the reproducing means has generally been in contiguous relationship with the disc. Actually, the reproducing means has constituted a needle which has contacted the groove in the disc to reproduce the information on the disc. This contact between the needle and the groove has tended to wear the disc after some copies have been made. .Iadd.